この前、一緒に料理を教えてもらって、ばぁばと色々話せて、すごく嬉しかったよ。
I heard this line in a TV drama, but I am bugged by the use of 一緒に in it. The protagonist says this to her ailing grandma by her deathbed. She recalls how her grandma taught her how to cook. I don't see how 一緒に is justified in this sentence since the protagonist is the only person that the grandma taught to cook. Including the listener, the grandmother, in the action (learning from Grandma) doesn't make much sense to me. In comparison, 勉強方法も一緒に教えてもらった (in addition to the content) and 母と一緒に先生に教えてもらってる both make sense because the clusivity in these two utterances matches the semantics. Why 一緒に here in the line at issue?
For reference, a clip of this scene can be found here, just in case I misheard it. The flashbacks also show one-on-one instruction. I thought of 一心に, but it doesn't seem like it either.